1 /* ir-rc6-decoder.c - A decoder for the RC6 IR protocol
2 *
3 * Copyright (C) 2010 by David Härdeman <david@hardeman.nu>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation version 2 of the License.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 */
14
15 #include "rc-core-priv.h"
16 #include <linux/module.h>
17
18 /*
19 * This decoder currently supports:
20 * RC6-0-16 (standard toggle bit in header)
21 * RC6-6A-20 (no toggle bit)
22 * RC6-6A-24 (no toggle bit)
23 * RC6-6A-32 (MCE version with toggle bit in body)
24 */
25
26 #define RC6_UNIT 444444 /* nanosecs */
27 #define RC6_HEADER_NBITS 4 /* not including toggle bit */
28 #define RC6_0_NBITS 16
29 #define RC6_6A_32_NBITS 32
30 #define RC6_6A_NBITS 128 /* Variable 8..128 */
31 #define RC6_PREFIX_PULSE (6 * RC6_UNIT)
32 #define RC6_PREFIX_SPACE (2 * RC6_UNIT)
33 #define RC6_BIT_START (1 * RC6_UNIT)
34 #define RC6_BIT_END (1 * RC6_UNIT)
35 #define RC6_TOGGLE_START (2 * RC6_UNIT)
36 #define RC6_TOGGLE_END (2 * RC6_UNIT)
37 #define RC6_SUFFIX_SPACE (6 * RC6_UNIT)
38 #define RC6_MODE_MASK 0x07 /* for the header bits */
39 #define RC6_STARTBIT_MASK 0x08 /* for the header bits */
40 #define RC6_6A_MCE_TOGGLE_MASK 0x8000 /* for the body bits */
41 #define RC6_6A_LCC_MASK 0xffff0000 /* RC6-6A-32 long customer code mask */
42 #define RC6_6A_MCE_CC 0x800f0000 /* MCE customer code */
43 #ifndef CHAR_BIT
44 #define CHAR_BIT 8 /* Normally in <limits.h> */
45 #endif
46
47 enum rc6_mode {
48 RC6_MODE_0,
49 RC6_MODE_6A,
50 RC6_MODE_UNKNOWN,
51 };
52
53 enum rc6_state {
54 STATE_INACTIVE,
55 STATE_PREFIX_SPACE,
56 STATE_HEADER_BIT_START,
57 STATE_HEADER_BIT_END,
58 STATE_TOGGLE_START,
59 STATE_TOGGLE_END,
60 STATE_BODY_BIT_START,
61 STATE_BODY_BIT_END,
62 STATE_FINISHED,
63 };
64
rc6_mode(struct rc6_dec * data)65 static enum rc6_mode rc6_mode(struct rc6_dec *data)
66 {
67 switch (data->header & RC6_MODE_MASK) {
68 case 0:
69 return RC6_MODE_0;
70 case 6:
71 if (!data->toggle)
72 return RC6_MODE_6A;
73 /* fall through */
74 default:
75 return RC6_MODE_UNKNOWN;
76 }
77 }
78
79 /**
80 * ir_rc6_decode() - Decode one RC6 pulse or space
81 * @dev: the struct rc_dev descriptor of the device
82 * @ev: the struct ir_raw_event descriptor of the pulse/space
83 *
84 * This function returns -EINVAL if the pulse violates the state machine
85 */
ir_rc6_decode(struct rc_dev * dev,struct ir_raw_event ev)86 static int ir_rc6_decode(struct rc_dev *dev, struct ir_raw_event ev)
87 {
88 struct rc6_dec *data = &dev->raw->rc6;
89 u32 scancode;
90 u8 toggle;
91
92 if (!(dev->raw->enabled_protocols & RC_TYPE_RC6))
93 return 0;
94
95 if (!is_timing_event(ev)) {
96 if (ev.reset)
97 data->state = STATE_INACTIVE;
98 return 0;
99 }
100
101 if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
102 goto out;
103
104 again:
105 IR_dprintk(2, "RC6 decode started at state %i (%uus %s)\n",
106 data->state, TO_US(ev.duration), TO_STR(ev.pulse));
107
108 if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
109 return 0;
110
111 switch (data->state) {
112
113 case STATE_INACTIVE:
114 if (!ev.pulse)
115 break;
116
117 /* Note: larger margin on first pulse since each RC6_UNIT
118 is quite short and some hardware takes some time to
119 adjust to the signal */
120 if (!eq_margin(ev.duration, RC6_PREFIX_PULSE, RC6_UNIT))
121 break;
122
123 data->state = STATE_PREFIX_SPACE;
124 data->count = 0;
125 return 0;
126
127 case STATE_PREFIX_SPACE:
128 if (ev.pulse)
129 break;
130
131 if (!eq_margin(ev.duration, RC6_PREFIX_SPACE, RC6_UNIT / 2))
132 break;
133
134 data->state = STATE_HEADER_BIT_START;
135 data->header = 0;
136 return 0;
137
138 case STATE_HEADER_BIT_START:
139 if (!eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2))
140 break;
141
142 data->header <<= 1;
143 if (ev.pulse)
144 data->header |= 1;
145 data->count++;
146 data->state = STATE_HEADER_BIT_END;
147 return 0;
148
149 case STATE_HEADER_BIT_END:
150 if (!is_transition(&ev, &dev->raw->prev_ev))
151 break;
152
153 if (data->count == RC6_HEADER_NBITS)
154 data->state = STATE_TOGGLE_START;
155 else
156 data->state = STATE_HEADER_BIT_START;
157
158 decrease_duration(&ev, RC6_BIT_END);
159 goto again;
160
161 case STATE_TOGGLE_START:
162 if (!eq_margin(ev.duration, RC6_TOGGLE_START, RC6_UNIT / 2))
163 break;
164
165 data->toggle = ev.pulse;
166 data->state = STATE_TOGGLE_END;
167 return 0;
168
169 case STATE_TOGGLE_END:
170 if (!is_transition(&ev, &dev->raw->prev_ev) ||
171 !geq_margin(ev.duration, RC6_TOGGLE_END, RC6_UNIT / 2))
172 break;
173
174 if (!(data->header & RC6_STARTBIT_MASK)) {
175 IR_dprintk(1, "RC6 invalid start bit\n");
176 break;
177 }
178
179 data->state = STATE_BODY_BIT_START;
180 decrease_duration(&ev, RC6_TOGGLE_END);
181 data->count = 0;
182 data->body = 0;
183
184 switch (rc6_mode(data)) {
185 case RC6_MODE_0:
186 data->wanted_bits = RC6_0_NBITS;
187 break;
188 case RC6_MODE_6A:
189 data->wanted_bits = RC6_6A_NBITS;
190 break;
191 default:
192 IR_dprintk(1, "RC6 unknown mode\n");
193 goto out;
194 }
195 goto again;
196
197 case STATE_BODY_BIT_START:
198 if (eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2)) {
199 /* Discard LSB's that won't fit in data->body */
200 if (data->count++ < CHAR_BIT * sizeof data->body) {
201 data->body <<= 1;
202 if (ev.pulse)
203 data->body |= 1;
204 }
205 data->state = STATE_BODY_BIT_END;
206 return 0;
207 } else if (RC6_MODE_6A == rc6_mode(data) && !ev.pulse &&
208 geq_margin(ev.duration, RC6_SUFFIX_SPACE, RC6_UNIT / 2)) {
209 data->state = STATE_FINISHED;
210 goto again;
211 }
212 break;
213
214 case STATE_BODY_BIT_END:
215 if (!is_transition(&ev, &dev->raw->prev_ev))
216 break;
217
218 if (data->count == data->wanted_bits)
219 data->state = STATE_FINISHED;
220 else
221 data->state = STATE_BODY_BIT_START;
222
223 decrease_duration(&ev, RC6_BIT_END);
224 goto again;
225
226 case STATE_FINISHED:
227 if (ev.pulse)
228 break;
229
230 switch (rc6_mode(data)) {
231 case RC6_MODE_0:
232 scancode = data->body;
233 toggle = data->toggle;
234 IR_dprintk(1, "RC6(0) scancode 0x%04x (toggle: %u)\n",
235 scancode, toggle);
236 break;
237 case RC6_MODE_6A:
238 if (data->count > CHAR_BIT * sizeof data->body) {
239 IR_dprintk(1, "RC6 too many (%u) data bits\n",
240 data->count);
241 goto out;
242 }
243
244 scancode = data->body;
245 if (data->count == RC6_6A_32_NBITS &&
246 (scancode & RC6_6A_LCC_MASK) == RC6_6A_MCE_CC) {
247 /* MCE RC */
248 toggle = (scancode & RC6_6A_MCE_TOGGLE_MASK) ? 1 : 0;
249 scancode &= ~RC6_6A_MCE_TOGGLE_MASK;
250 } else {
251 toggle = 0;
252 }
253 IR_dprintk(1, "RC6(6A) scancode 0x%08x (toggle: %u)\n",
254 scancode, toggle);
255 break;
256 default:
257 IR_dprintk(1, "RC6 unknown mode\n");
258 goto out;
259 }
260
261 rc_keydown(dev, scancode, toggle);
262 data->state = STATE_INACTIVE;
263 return 0;
264 }
265
266 out:
267 IR_dprintk(1, "RC6 decode failed at state %i (%uus %s)\n",
268 data->state, TO_US(ev.duration), TO_STR(ev.pulse));
269 data->state = STATE_INACTIVE;
270 return -EINVAL;
271 }
272
273 static struct ir_raw_handler rc6_handler = {
274 .protocols = RC_TYPE_RC6,
275 .decode = ir_rc6_decode,
276 };
277
ir_rc6_decode_init(void)278 static int __init ir_rc6_decode_init(void)
279 {
280 ir_raw_handler_register(&rc6_handler);
281
282 printk(KERN_INFO "IR RC6 protocol handler initialized\n");
283 return 0;
284 }
285
ir_rc6_decode_exit(void)286 static void __exit ir_rc6_decode_exit(void)
287 {
288 ir_raw_handler_unregister(&rc6_handler);
289 }
290
291 module_init(ir_rc6_decode_init);
292 module_exit(ir_rc6_decode_exit);
293
294 MODULE_LICENSE("GPL");
295 MODULE_AUTHOR("David Härdeman <david@hardeman.nu>");
296 MODULE_DESCRIPTION("RC6 IR protocol decoder");
297